The invention relates to a welding wire, rod, stick, or the like, of novel microstructural configuration, and to techniques for its manufacture.
It is known that by extrusion, rolling or squeezing, and more generally by hot or cold working, two metals of the same or different kind, can be joined together. It is also known that particulated matter can be compacted under pressure so as to become a unitary mass or body.
The present invention essentially relates to a novel microstructural configuration for a filler wire, rod, or stick typically used in welding operations. It consists of an elongated member of material of a precise and required composition which is melted by the applied heat in the course of the welding operation so that a bead of molten material is progressively yielded to fill the gap along the welding line. Three factors are of importance for such filler materials.
(1) The filler material must have a precise chemical composition in order to properly unite the two parts of the workpiece to be welded and form a seam when consumed.
(2) The material melted by the welding heat source must be a metal alloy of precise composition and structure.
(3) The filler wire must have the required cross-section, and be of a length sufficient to be fed regularly by the operator and supply the desired amount of filler along the seam. A correlative requirement is that the wire, rod, or stick have sufficient mechanical strength and ductibility to be packed, or wound, stored, transported and automatically fed by the welding apparatus.
In order to solve this problem, the prior art in the context of a metal composition has taken two avenues: metallurgical or mechanical alloying.
Forming a rod, wire or stick by mechanical alloying consists in building a metal sheath around a core of particulated alloy by continuous rolling or in forming a ceramic coating with such particulated alloy by cold working or by extrusion around a core of wire.
Metallurgical alloying involves alloying in the initial melting stage to obtain the desired metal composition. The alloy thus formed is then cast into an ingot, and the ingot is hot-worked to form the rod. An ultimate cold-working step combined with annealing changes the rod into a wire. It is clear that the mechanical and metallurgical methods are complex and costly methods of fabricating welding filler wires.
The object of the present invention is to provide a simpler, less expensive, wire, rod and/or stick suitable for filler applications in welding processes.
The filler material, for certain welding applications requiring the addition of a flux to prevent oxidation and other chemical contamination at the welding seam, the wire, rod, stick, or the like according to the present invention may be a composite material including a fluxing agent.
It is known from U.S. Pat. No. 1,972,463 to make rods or wires containing the fluxing agent in a finely-dispersed state throughout the material. To this effect, mixtures of powdered metal and fluxing agent are sintered in suitable molds to be brought into the form of rods or wires for welding application. Metal powder is obtained from metal carbonyl and sintering is performed on the metal powder with the finely-divided flux by means of heat or mechanical pressure, or both, to form the wire without a melting operation. This patent merely reveals the problems encountered when a fluxing agent is added, since the agent should not melt at the early stage of forming the rod, or wire, and the particles of agent should be intimately embedded in what should be a rod or wire. Still, the production of such rod, or wire by merely agglomerating together under pressure a mixture of particulated materials, will not yield a high density composite metalic structure having on the one hand the required mechanical quality to become, as a welding wire, or rod a staple article, nor which can be easily fed in an automatic welding machine of the marketplace, nor which can be identified by its chemical composition and final alloy microstructure (e.g. after being consumed in the welding process). For these reasons, the prior art does not teach or suggest the filler wire, rod, stick, and the like, with or without fluxing agent, according to the present invention.